Lucio’s Phenomenon

Abstract

Lucio’s phenomenon (LPh) or erythema necroticans is the acute reaction that develops in patients with diffuse lepromatous leprosy or pure and primitive leprosy or lazarine leprosy or Lucio–Latapí leprosy, which is a systemic and peculiar form of leprosy, a polar lepromatous type of the disease in which the patient has no response to lepromin skin test, has no lepromas but diffuse infiltration of the whole skin, and is multibacillary. Lesions in LPh are infarcts due to the necrotizing panvasculitis that takes place in these patients; medium-sized arteries, arterioles, capillaries, venules, and veins are involved in one way or another during this process; histopathologically there is wide infiltration by macrophages filled with acid-fast bacilli, probably of a particular strain named Mycobacterium lepromatosis.